Following a run of poor form earlier in the season, Szczesny saw his starting berth handed to fellow Poland international Fabianski, only for the latter to sustain a cracked rib during the 3-1 win over Norwich on Saturday.

The injury saw Fabianski miss a 0-0 draw with Everton on Tuesday, with his compatriot returning after a five-game absence, and Szczesny will continue between the posts for the trip to Fulham.

"Lukasz has a crack in his rib that has not moved," Wenger told reporters.

"That means we have to treat it clinically. That means has he pain or not? That is day by day. I don't know when he'll be back."

Szczesny was rested - in what Wenger called "a breather" - last month due to an erratic run of form, with the manager suggesting the pressure he was under may have affected his confidence.

During his absence, Szczesny failed to make the bench for the Champions League last-16 tie against Bayern Munich, or Premier League games against West Brom and Norwich, with Vito Mannone used as cover.

But the 23 year-old impressed against Everton, with Wenger praising Szczesny's positive reaction to being dropped.

Wenger said: "He had a good performance against Everton. I was pleased with his focus, with his sharpness. He dealt well with the situation that he faced.

"In our job, there is only one way to respond, which is to practise harder and stronger and show that you are ready for a fight. That is what he did."